Electrical wiring panel



Oct 1952 F. s. WALTERSDORF ETALQ 3,306

ELECTRICAL WIRING PANEL 2 SHEETS-SHEET 1 Filed Feb. 28, 1949 Inventors: Felix 5. Waltersdor Robert W 'Scxa'ba"; Frank T Grothcu hei Y A'tt Oey.

Oct. 7, 1952 F. s. WALTERSDORF Er AL ELECTRICAL WIRING PANEL 2 SHEETS-SHEET 2 Filed Feb. 28, 1949 Inventors: I Felix S. Waltersdorfi Robert W. Scott Frank T GrOthQuse,

Then Att 0 rney.

Patented Oct. 7, 1952 ELECTRICAL WIRING PANEL Felix S. Waltersdorf, Bridgeport, and Robert W. Scott, Milford, Conn, and Frank T. Grothouse, South Euclid, Ohio, assignors to General Electric Company, a corporation of New York Application February 28, 1949, Serial No. 78,738

Our invention relates to electrical heating devices of the radiant heating panel type.

For heating surfaces and enclosures, a broad field of application and use exists for a heating device in the form of a panel which may be attached to any surface; for such a heating panel whichis thin, light, and flexible so that a group of such panels may be readily adaptable to conform to the configuration of the surface to be ,heated; for a heating panel, readily controllable with respect to the rate of heat radiation; and for such a heating panel which has a low thermal mass so that the heat emanating from the panel. may be immediately responsive to changes in heating requirements. Accordingly, it is a primary object of our invention to provide a heating panel of the electrical type which is thin and flexible and is readily adaptable to any type of surface, and which has a low thermal mass so that the total heat radiated is readily controllable and immediately responsive to the changing requirements for heating.

Electrical heating panels as disclosed by this invention find many uses such as heaters for de-icing airplane wings, table-top heaters for keeping food warm, for incubators, baby cribs,

warmth and comfort if the surrounding surfaces of the enclosure are warm, even though the temperature of the air within the enclosure is relatively cool. An explanation of this is that if the surrounding surfaces, such as the walls, ceiling, and floor are heated,the body of the person then radiates heat at a reduced and controllable rate to the surrounding surfaces so as to impart a feeling of warmth in the person. Moreover, heat radiated from the surrounding surfaces produces a feeling of warmth when it strikes a person even though the intervening air has not been appreciably heated thereby. It is therefore a further object of our invention to provide electrical heating panels particularly suitable for use in houses, offices, or other enclosed spaces.

It is a further object of our invention to provide electrically heated panels having sufficient strength to withstand rough usage, and which are completely moisture resistant.

' It is also an object of our invention to provide a new and improved electrical heating panel construction so that a plurality of panels may be employed in any given application, and to provide for the supply of electrical power 119 each 4 Claims. (Cl. 219-49) adaptable for aifixation to a surface.

, 2 I of the panels without detracting from the appearance.

For such electrical heating panels to be commercially feasible, it is important that the cost of production be minimized. This necessitates,

in particular, a method of manufacturing so that the panels may be fabricated by machine in-a continuous process. Therefore, it is an object of our invention to provide a new and improved heating panel structure, which is particularly adaptable to continuous production. v

To this end, the important features of our invention consist in constructing an electrical heater in the form of a thin flexible panel having an electrical resistance element insulated and sealed between outer protective coverings, so that the resultant electrical heater is impervious to moisture, resists physical shock, and is readily Further, an improved construction is provided for conducting electric power to the panels through a conduit which also serves as a means of anchor- .nga portion of each panel on a surface. Our invention will be better understood from the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring to the drawings Fig. 1 illustrates a cut-away'portion of an enclosure, such as a room, showing one embodiment of our invention in which heating panels are installed on the wall portions of the enclosure; Fig. 2 illustrates schematically' one'step in the production of a heating panel; Fig. 3 illustrates schematically an alternative method for fabricating these electrical heating panels particularly adaptable to production by machine; Fig. 4 is an enlarged cross-sectional view of a'portion of a partially completed heating panel; Fig. 5 is a cross-sectional view of a portion of a completed panel; Fig. 6 is an enlarged cross-sectional view of a portion of a completed panel showing a contact strip in position; Fig. 7 is an exploded view of a section of a panel illustrating the construction and method of mounting of the terminal. elepartially broken away, to illustrate the construction of the contact block shown by Fig. 10; and Fig. 12 is a cross-sectional view taken on the line 12-42 of Fig. 11.

.iniurv.

The specific form of the invention shown in the drawings is particularly suitable as a means for radiant heating of an enclosure, such as a home or ofiice. In Fig. 1, there is illustrated. a portion of an enclosure having a floor l, walls 2, and a ceiling 3. A series of electrical heating panels 4, made in accordance with our invention, are mounted on the walls of this enclosure for the radiant heating of the enclosed space. As here shown the panels are installed in abutting relation. However, the panels may also be mounted in spaced relation covering only part of a surface. These heating panels 4 may be secured in place by any suitable method. As shown, a baseboard 5 maintains the lower portion of the panels in proper position, and the upper portion of each panel is held in its proper position by suitable fastening devices extending through a conduit 6 and into the wall as will be explained later. The conduit 6 provides not only a suitable molding between the walls and. ceiling of the enclosed space, but also a convenient and concealed space for power supply leads I and 8. At appropriately spaced points contact or connectiondevices 9, are inserted between adjacent sections of the conduit 6, for conducting power from the power supply leads 1 and 8 to the terminals of "resistance elements imbedded within panels 4. It will be understood, of course, that many other methods might be employed for attaching or afiixing the heating panels to a surface; for example, other methods are to employ a suitable glue or cement between the panel and the surface on which the panel is mounted, or by use of a cement-coated tape hich adheres to the panel and the surface on which the panel is-mounted.

It is essential in the construction of an electrical heating panel that the resistance element be insulated from the wall to which it is external, and from'the'outer surface of the panel itself, so that dan er of fireor electrical shock is substantiallv eliminated. Furthermore, the electrical heatin element must be secured firmlv in position and protected from moisture and phvsical A form of heating panel constructed in accordance with this in ention comprises a pluralit 'of sheets of insulation having an electric heatin grid sand iched bet een opposed surfaces of the sheets, the sheets and grid being bonded together by a resinous material.

Referring to Fig. 2, one step of amethod for producing such an electrical heating panel is shown. In this method, :an electrical heating element In is arranged in a serpentine form, althou h other arrangements or configurations of this heating element or grid may be eoually suitable. However, toinsure a uniform heat over the entire surface of the completed panel, the spacing of the resistance wires should be regular and with no large unheated areas on the panel. We

found in one construction that a spacing of one quarter inch between the conductors, measured along the longitudinal center line of the panel, as shown by Fig. 2, produces a panel with uniform heating over the entiresurface. Such spacing, of course, mayvary depending upon the temperature to which the panel is to be heated, and

In actual practice, the heating grid is first properly oriented on the lower sheet H. The insulating sheets II and I2 may'be paper or cloth 4 properly treated for use as insulators, or any other thin flexible material capable of serving as an electrical insulation. These sheets of insulation I I and I2 are coated or impregnated with a plastic compound. By the term plastic is meant any one of the natural or synthetic resinous compounds of the thermoplastic or thermo-setting type, as well as any one of the natural or synthetic rubbers. To mount and sup- ;port the heating element l0, therefore, the heating element is placed on the plastic coated insulating sheet ll. Sheet I2 with its plastic coatingpnits underside, or the side in contact with the heating element, is placed over and in coterminous relation with sheet II. This assembly is thensubjectedto heat and pressure so that the heating .element H! is securely bonded between the sheets I! and I2. If a thermo-plastic bondingmaterial is employed, the bonding takes place, of course, upon cooling of the assembly; however, .it maybe preferable to. employ a thermosetting .resinouslcompound .in an uncuredlor partially uncured state, so that upon the application of heat and pressure, the .final curingof such thermo-setting compound takes place, ,resulting in the bonding of the heating element between the insulating sheets. r

In order to produce these heating .panels economically, a continuous processis needed for securing the electrical heating .element between the sheets of .insulationmaterial. Such amethod of continuous fabricationis illustrated by Fig. 3. In accordance with this method, sheets of insulating fabric or paper aresuppl-ied from a lower roll 13 mounted on a spindl l4; and from van upper roll l5 rotatable on its spindle Hi. The insulating material carried by both the rolls l3 and I6 has a'suitable plasticcoating on its outer surface. As in .theapplication described in connection with Fig. 2, this plastic coating may be of either thermo-plastic or thermo-setting material. The insulating material from the lower roll 13 is passed over a lowerpressure-roller I! which is rotatable on its spindle l8. Roller -l-1 has two parallelrows wand 20 of projecting pins on its cylindrical surface. The tension on completed strip 2| causesthe projecting pins Hand 20 to pierce insulating sheet 22 coming from the lower roll [3, so that a portion of the projecting pins are exposed. A resistance wire 23 coming from spool 24 may then be woundback and forth between these rows .of projecting pins I9 and 20 toform a serpentine heating element orgrid 25.

- An upper pressure-roller 26, rotatable on a spindle 2! and mounted contiguous to the lower pressure roller ll, contains a pair of grooves 28 and, 29 which are aligned with the rows of projecting pins 19 and 20, so that upon rotation of rollers I! and 26 there is no interference caused by these projecting pins. Any suitable means may then be employed for heating the lower and upper pressure rollers Hand 26,,so thatas the two sheets ofinsulating material with the resistance element therebetween pass betweenrollers I! and 25, both heat and pressure are applied, bonding the two sheetsof insulating material to each other and to the resistance element 25. While we have illustrated this preferred apparatus for performing this method offabrication of the sealed heating unit, other forms of apparatus may, of course, be employed toperform the same or similarfunctions. For example, the resistance wire 23 may be wound about the rows of projecting pins i9 and 20 by hand, .or this same function may be accomplished by anautomatic mechanical means.

'- the plastic coating may be softened by use fof a solvent or by induction heating rather than by heating rollers H and 26. The completed strip 2| emanating from between the rollers ii and 26 is cut into suitable lengths, and terminal leads 3!! and 3l, such asshown by Fig. 2 are left exposed for connection to a power source.

In accordance with the method illustrated by i Fig. 3, the resistance wire 23 is initially held in its proper position by the tension on the wire as it is wound back and'forth between the parallel rows of projecting pins 59 and 29. However, as the heating element or grid 25 and the two sheets of insulating material from rolls l3 and 55 come between the upper and lower pressure rollers H and 26, the pressure of the rollers will hold the resistance wire in its proper position. If a thermo-setti s plastic material is employed as the coating for the two sheets of insulating material, the heat applied to the pressure rollers I! and 26 is so adjusted, and the speed at which the completed product comes from rolls H and 26 is so controlled, that the thermo-setting plastic material sets before the pins are withdrawn. If a thermo-plastic material is employed, the speed of rotation of rollers IT and Z6 andthe amount of heat applied are regulated so that the plastic material is softened sufficiently to allow the bonding of the two sheets to each other and to the reistance wire before the projecting pins are withdrawn. It is thus seen that a continuous strip process-is provided for the manufacture of a sealed and insulated heating element.

F For most applications of heating panels in accordance with this invention, additional insulation and a more or less rigid outer covering are required, although the completed product as illustrated by Figs. 2 and 3 may be suitable for certain applications. constructed in accordance with a preferred em- Fig. 4. illustrates a panel bodiment of our invention. Referring to Fig. t, the resistance wire comprising the heating element for the panel is shown at 25, and the two sheets of plastic coated insulating material bonded to each side of the heating element are shown at;30a and sla. The method of manufacture of this portion of the completed panel has been described above in connection with Figs. 2

,. and 3. In the embodiment shown in Fig. 4, additional sheets of insulating material 32 have been 1 added. Insulating material 32 may be of any suitable type, such as paper impregnated with a suitable insulating compcund. To provide the re .quisite strength and to protect the heating ele ment from physical damage, outer protective coverings 33 and 3 preferably of metal, are emthat resistance wires 25 are firmly imbedded in a homogenous mass of insulation 35 which in turn is sealed between the outer protective coverings 33 and 34. The outer protective coverings may be of' any suitable thermally conductive material; however, we have found that the maximum strength and protection is provided for the panel by using a metallic layer for this covering. Thin sheets of aluminum form a highly satisfactory protective covering, since aluminum is light, strong, and free from corrosive eifects, provides I -a covering which readily transmits the heat from end, we provide a terminal struoturefo'r each panel, with each terminal or contact member for conducting electrical power to the panel heating elementsubstantially flush or coplanar with the surface of the panel. Fig. 6 illustrates this construction of a completed electrical heating panel having outer protective coverings 33 and 3 5, a mass of insulating material 35, a lead 38 coming from the electrical heating element, and a contact strip Bl connected to this lead. The details of this construction will be more clearly understood by a reference to Fig. 7, showing the outer protective coverings 33 and 34, the assembly 38 of the heating element bonded between sheets of insulating material, and the additional sheets of insulating material 32. In fabricating the heating element between the two sheets of insulation, leads of an appropriate length 39 and to extend from the heating element and lie outside of the bonded sheets of insulation material covering the heating element. Contact strips or terminals M and d2, of aluminum, copper, or

panel, the terminal 4! is bent over.

other suitable electrical conducting material, are secured to the ends of theleads 39 and 49. Initially these terminals ll and 42 aresubstantially L-shaped. One portion of the terminal is then rolled around its associated lead, and pressure is applied so that the terminal is permanently attached to the lead. In addition to or in lieu of rolling this contact strip around the lead and ap lying pressure, solder may be employed to insure a permanent contact and connection between the lead and its terminal.

A'portion of one of the outer protective coverlugs 33 is cut out, as shownat 43, in order to provide a space on the surface of thepanel for the two panel terminals. A dielectric plate 44 is provided as a mounting block for the terminals. The dielectric plate 634 is of fabric or heavy impregnated paper, and it may be cut the same size as the cut-out portion 43; or as shown in Fig; '7, the dielectric member 44 may be slightly larger than the cut-out portion 43cc that it is anchored in position by the outer covering 33. A slot 35 is provided in dielectric "member 44 through which theterminal 4! may project. Similar slots are provided, of course, in the additional sheets of insulation 32. In assembly the terminal M is forced through this slot 45, and then while pressure is applied to the assembled The free end of terminal M is then forced downwardly through a slot 46. Likewise terminal i2 is forced through a slot ll and similar slots in the additional sheets of insulation 32, and'as pressure is applied the strip i2 is bent over and its free end is forced downwardly through a slot 48. Finally,

when heat and pressure are applied to the assembled panel, dielectric member M is sealed in position with the terminals ii and 32 approximately flush with the surface of the panel. The completed panel will appear as shown in Fig. 6 with the terminal 31 attached to the lead 36 from the electrical heating element, and with the terminal bent over and forced downwardly into the insulation; and after the heat and Pressure have been applied, this terminal 3'! is firmly anchored with only a flat contact surface exposed. In Fig. 8' a completed panel 49 is shown with the heating element 25 sealed in position,

. 7 ---andconnected by.-leade--39- and to contacts" 50 and St-mounted-onan insulating plate which is'securedwithin-- a cut-out portion 43 of the protective covering ofthe panel.

By-employing-surfacecontacts 50 and l the 1 installation and connection of the power supply -.-to--the panels is facilitated. Figs. 9 through 12 mil-lustrate a-preferred-arrangement for supplying -=power-to-thepanelsfthe arrangement shown be- -ing-theinvention of-Clarence Frere and being disclosed and-claimed in his application, Serial No. -.-195,845,- filed-November 15,1950, and assigned to 1 the same -assignee as --the instant application.

described. in-connectionwith Fig.1,- the power asupplyrmeans for agroup orinstalled panels --s appers-only asamolding. shownin Fig. 9,

-.; the-panel 4 is provided-with a series of'apertures 52 tand=corresponding apertures are-provided in --.conduitbases53 and 54 so that bymeans-of any suitable fastening devices, such as screw-thread- --ingapertures 56 and 51 are provided on the panel 4-,- and cooperating projections on the back side of the terminal block 55; as shownby Fig. 10, are engagedin these apertures 56 and 51- to hold the terminal block-accurately in position.- Conduit covers 58-and59 are designed so. that they engage the conduit bases 53 and 54 with a press fit to cover the conduit bases .and the terminal block. 'Both the base andthe cover for each of-these conduits are made preferably of steel, so that the fnatural resiliency of these parts will: hold them together. The dimensions of terminal block'55 are so proportioned with respect to the dimensions of the conduit bases 53 and 54, that the conduit bases -fit over theterminal block with a force L fit. The. power supply leads lie within the conduit, andthe terminal block 55 is provided with --parallelrecesses .60 and 6| forthe reception of thesepowerleads. A cover 62 is removably-secured to terminal block- 55 to retain the conductors oftheelectrical supplyline in position, and

thiscover serves theadditional function of permittingready-inspectionof the power leadsand .--their-connections. Threaded bores 63 and--54 are providedin'terminal block 55 so that screws 65 .and 66 may be passedx-through cover 62' and threaded into these bores 63 and 64 to holdcover -62 in position.

In Fig. the contact making'device is shown assembled with a panel, and Figs. 11 and *12 show further details. To accurately position this de- .-vice with respect to the panel, and to provide a ---means for attaching-the cover '62 to the body member -55, tubular -members 61'- and t8 are --.-.-mounted inand form a part of body member 55. Eachof these tubular members 61 and 68-in- --5c1lld8S a threaded portion as at 69 and 10, and it is this portion of each tubular member which results in the threaded bores'63 and 64. In addition, tubular members 6'! and 68 each have a slightly flared portion I l -and12, so that once the -terminal block is mounted on the panel it will v beheld in its proper position. The leads for conducting power to the panel comprise the conductorsl3-and 14 covered by insulation and 16. Withthe cover 'fi2 removed the power supplyleads 7 may be 'positionedwithin the; parallel grooves or recesses Hand '6 l of rthe-body memb'er 55. The

/ body member 55*has integrally'formed therein pin members 11 and 18-, corresponding respectively with'recesses SI and 60 for the conductors of the electrical supply -line.- Eachpin member-has a contact portion 19 which makes contact with the corresponding terminal 50 or 5| on the heating panel;-and=each contact portion 19 is connected by a strip 80 to a spike 8 l Spikes 8| pierce the'in- -su1ation-15-and16 onthe power supply conductors to complete the electrical circuit fromthe electrical supply line to: the heating elementln the panel. Thus, toestablish this connection it is only necessary to-mount the contact making device-in its proper-position on the panel and lay the conductors within the recesses 60 and il.- When the terminalblockcover is placed inpositionand the screw-threaded fasteners are tightened down, the powersuppl-yconductors will be forced against the: spikes 8| resulting in the connection tothe -heatingelement of the panel. Body member 55 of thecontact making devicemay be made otany suitable insulatingmaterial, preferably a molded phenolic condensation product, such as Bakelite. Tubular members 61- and'68, of a'metal -such'as brassorsteel, may be positioned in memberduring the moldingoperation. Likewise the pin members Hand 18, of electrical conducting material are mounted in member 55.; The strips 80 which connect spikes'BI to contacts 19 in the contact making device may be of copper or other-electrical conducting material-,orof a conducting 1 metal which will fuse and breakthe electrical circult to the heating panel in case-of overloador I short circuit. It will thus be seen-that an arrangementis provided for supplying power-to each panel which is-convenientto installaandis ot pleasing appearance," while insuring a-positive contact between the power'supply leadswandthe heating panel.

While no arrangementhas been shown for controlling the power supply to the installed panels 1 through leads 1 and 8, it will be understood that normally some type of heat'responsive controller will be installed between the main electrical power source and leads 1' and 8, such as a thermostatically controlled contactor. No complicated mechanism for this control is required since a-simple switching mechanism may be employed to'open and close the circuit to' the panels and thus regulate the heat output. *By reason of the fact that the thermal mass of the panels, in accordance with this'invention, has been reduced to a practical minimum, the heat emanating from the panels will be quickly responsive to a controlling thermostat.

While we have shown particular embodiments of the various phases'of our invention, it will be understood; of course, that we do not wish to be limited solely thereto since modifications may be made, and we, therefore, contemplate by the ap- "pended claims to cover'any such modifications as :fall within the true. spirit andisco'peof curlinwvention.

"What we. .claimfasnew and desire-.to' sec'ure by "Letters Patent of the United'States" is:

. 1. An electric heating 'panel' comprising a plurality of" sheets iof 'insulating materiaL'; a grid of resistance: wire positioned-"betweenmpposed surfaces of saidsheets; thermally -conductive-rlayers positioned on the-other surfaces of said sheets,

by a plastic material one of said layers having acut-out-portion-therein,said wire having a pair of terminals located in said portion, a dielectric member for supporting said terminals in spaced relation and positioned in said cut-out portion, said dielectric member and said terminals having outer surfaces substantially coplanar with the outer surface of said one layer.

2. An electric heating panel comprising a plurality of sheets of insulating material, a grid of resistance wire positioned between opposed surfaces of said sheets, metallic layers positioned on the other surfaces of said sheets, said sheets and said layers being bonded together by a plastic material, one of said layers having a cut-out portion therein, said wire having a pair of terminals located in said portion, a dielectric member positioned in said cut-out portion for supporting said terminals, said dielectric member and said terminals having outer surfaces substantially coplanar with the outer surface of said one layer.

3. A heating panel comprising a plurality of sheets of insulating material, an electrical heating grid positioned between opposed surfaces of said sheets, means for bonding said grid between said sheets of insulating material, thermally conductive layers afiixed to the other surfaces of said sheets, one of said layers having a cut-out portion therein, said grid having a pair of terminals located in said portion, a dielectric member positioned in said cut-out portion, said terminals being supported in said dielectric member with Y the outer surfaces of said terminals substantially coplanar with the outer surface of said one layer.

4. In an electric heating panel of the type having a heating grid sealed between insulating and protective layers with terminal leads extending from the grid between two of the layers, a contact structure adapted to be connected to the terminal leads for supplying electrical power to the grids, said contact structurecomprising a fiat strip of electrical conducting material connected to each terminal lead, a dielectric plate having a pair of spaced slots for each strip, each strip extending outwardly from the panel through one of its corresponding pair of slots and inwardly of said plate, and means bonding said plate to an outer layer of the panel.

FELIX S. WALTERSDORF. ROBERT W. SCOTT. FRANK T. GROTHOUSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 761,204 Carpenter May 31, 1904 1,144,224 Mills June 22, 1915 1,376,987 Wirt May 3, 1921 1,514,618 Ide Nov. 11, 1924 1,521,241 Hale Dec. 30, 1924 1,597,257 White Aug. 24, 1926 2,025,540 Langley Dec. 24, 1935 2,293,596 Del Camp Aug. 18, 1942 2,301,288 Knauf, Jr., et al. Nov. 10, 1942 2,314,766 Bull et a1 Mar. 23, 1943 2,314,855 Del Camp Mar. 23, 1943 2,408,045 Cottrell Sept. 24, 1946 2,419,652 McLarn Apr. 29, 1947 2,445,587 Sims July 20, 1948 2,502,148 Grothouse Mar. 28, 1950 2,512,875 Reynolds June 27, 1950 FOREIGN PATENTS Number Country Date 224,648 Great Britain Nov. 20, 1924 1 384,382 Great Britain Dec. 8, 1932 393,304 Great Britain June 1, 1933 469,744 Great Britain July 30, 1937 

